This invention relates to a protective sleeve for use with a pipe coupling that couples together the ends of grooved pipes.
An example of such a type coupling is disclosed in my U.S. Pat. No. 4,966,395 issued Oct. 30, 1990 for a "Rigid or Flexible Coupling for Pipes." Similar types of couplings used for coupling adjacent pipe ends are disclosed in U.S. Pat. No. 4,915,418 issued Oct. 10, 1990 to Josef Palatchy for a "Hinged Pipe Coupling," and U.S. Pat. No. 5,018,768 issued May 28, 1991 to Josef Palatchy for a "Pipe Coupling Hinge." Numerous other prior patents disclose commonly used pipe coupling formed of two or more curved segments which are connected together end-to-end to form a circular coupling which is arranged to surround a pair of aligned pipe ends for joining the pipe ends together. This type of coupling device is U-shaped in cross-section to provide parallel, radially inwardly extending legs whose continuous, free, edges form keys. These free edges or keys fit into circumferentially arranged grooves provided near the free ends of the pipes to hold the pipes together. Normally, a rubber-like gasket is arranged within the coupling and surrounds the adjacent ends of the pipes for sealing them together.
Such couplings are commonly used in water distribution systems, as for example, for sprinklers systems within buildings, and other systems for conveying liquid. The pipes used in the particular system may be formed of metal or plastic materials. The couplings are normally formed of metal.
The keys of the couple engage locations on the walls or base of the pipe grooves and exert a pressure against these locations. The pressure may be exerted in a longitudinal direction against the walls forming the grooves in the pipes or in a radially inwards direction against the bases of the grooves in the pipes, depending upon the size and shape of the keys of the coupling or the grooves in the pipes. When the coupling segments are fastened together, such as by bolts securing adjacent ends together, the radially inwardly directed forces of the keys against the bases of the pipe grooves or the longitudinally directed forces of the keys against the walls of the couplings, are readily absorbed with normally no damage to the pipes as long as the forces exerted by the keys are limited.
Where plastic pipes are used, the plastic materials that form the grooved pipes normally do not have sufficient strength to resist key pressures resulting from overtightening the fasteners of the segments. That is, excessive key pressure on the pipe groove walls or bases can damage the pipes at or near the locations engaged by the keys. Thus, the amount of manually applied force used to connect the segments by bolts or other fasteners, must be carefully controlled to avoid overtightening which would otherwise damage the pipe ends and their grooves. Normally, the installer of a piping system limits the amount of forces applied to the fastening bolts or other types of fasteners to the point where the couplings do not damage the pipes themselves. But, there are instances where overtightening inadvertently occurs and damage results.
Similarly, this problem arises where thin wall metal pipes are used in a piping system. Moreover, it is normally not feasible to connect together a relatively stronger metal pipe with a relatively weaker plastic or metal pipe because normally, frequently, more forces are applied to the coupling segment fasteners when a stronger metal pipe is involved. That may be due to the need for tighter clamping around a heavier metal pipe or may be due to carelessness or inattentiveness on the part of the installing tradesman in overlooking the need to carefully limit the forces because of the weaker pipe. In any event, coupling a weak plastic to a strong metal pipe frequently results in the coupling device damaging the plastic pipe because the forces that would normally be absorbed by the metal pipe are sufficient to cause damage to the plastic pipe groove walls or bases or crack or crush the plastic pipes.
Thus, there is has been a need for a means to protect plastic pipes against damage caused by overtightening of coupling segments around the plastic pipe and, particularly, to protect relatively weaker plastic or metal pipes sufficiently so that they may be cou0led to relatively stronger metal pipes without damage to the weaker pipes.